Winter Weather Advisory 13, NWS Anchorage, AK

667 
WWAK41 PAFC 201357
WSWAER

URGENT - WINTER WEATHER MESSAGE
National Weather Service Anchorage AK
457 AM AKST Sat Feb 20 2021

AKZ171-202100-
/O.CON.PAFC.WW.Y.0013.000000T0000Z-210220T2100Z/
Kodiak Island-
Including the city of Kodiak City
457 AM AKST Sat Feb 20 2021

...WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL NOON AKST
TODAY...

* WHAT...Snow occurring. Additional snow accumulations of 2 to 3
  inches.

* WHERE...Kodiak Island.

* WHEN...Until noon AKST today.

* IMPACTS...Plan on slippery road conditions.

* ADDITIONAL DETAILS...Snow intensity should increase once again
  around daybreak. Light snow could continue to linger into the 
  evening, but snow rates and accumulation will taper off after 
  noon.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Slow down and use caution while traveling.

For the latest road conditions call 5 1 1 or visit
511.alaska.gov.

&&

$$

http://www.weather.gov/afc

359 
WWAK41 PAFC 202110
WSWAER

URGENT - WINTER WEATHER MESSAGE
National Weather Service Anchorage AK
1210 PM AKST Sat Feb 20 2021

AKZ171-202215-
/O.EXP.PAFC.WW.Y.0013.000000T0000Z-210220T2100Z/
Kodiak Island-
Including the city of Kodiak City
1210 PM AKST Sat Feb 20 2021

...WINTER WEATHER ADVISORY HAS EXPIRED...

Conditions are improving in Kodiak. However, expect light snow to
continue through the evening.

$$

http://www.weather.gov/afc

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
544 AM AKST Fri Feb 19 2021

.ANALYSIS AND UPPER LEVELS...

An impressive Arctic trough is making headway across the mainland
into Southcentral this morning as it digs southeast and leads to
rapid 500 mb height falls. Very strong cold air advection is
accompanying this wave, with temperatures quickly falling from the
20s and 30s that were in place over much of Southcentral on
Thursday evening down now to the 10s across all but the North Gulf
Coast. An even colder air mass has overspread the Southwest, with
many inland locations now reporting temperatures well below zero.
Outflow winds are picking up near the coast, including areas
around Whittier and Seward. Much stronger winds are blowing
through the Kamishak Gap into the Barren Islands, with gusts well
into storm force range recently observed in the area.

Out in the west, a front is progressing across the central Bering
and Aleutians behind an upper ridge in place over the eastern
Bering. The front is beginning to decelerate as it encounters the
deeply entrenched Arctic air mass over the northern Bering and
Southwest. Snow and gusty southeast winds are spreading into the
Pribilofs along and ahead of the front, and the winds combined
with falling snow are leading to blowing snow and poor visibility
over the islands. These conditions should continue or worsen as
winds continue to increase this morning ahead of the approaching
front.

&&

.MODEL DISCUSSION...

Models remain in reasonable agreement at the synoptic level, but
smaller scale details, especially towards the Southwest/Bering, remain
somewhat unclear. Models continue to struggle with the
development and progression of a triple point low forming by
tonight along the front currently tracking across the Bering. The
NAM/GFS initially form the center north of the Eastern Aleutians
or southern AKPEN and have it track very close to Kodiak Island by
early Saturday, while the EC/Canadian develop and track the low
farther south and are a bit less progressive with the low as it
approaches the Gulf. This is resulting in significant uncertainty
for snowfall timing and amounts near Kodiak for early Saturday.
Similar issues arise with a second low moving in from south of the
AKPEN to near Kodiak Island by late Saturday into Sunday, and
there are lingering questions regarding precip type with the
second low track also remaining somewhat uncertain. Given these
factors, confidence remains lower for this portion of the
forecast, particularly across the AKPEN and around Kodiak Island
through the weekend.

&&

.AVIATION...
PANC...VFR conditions are expected to prevail for the TAF period.
North winds around 10 to 15 kts with gusts up to 25 kts will
decrease throughout the morning and early afternoon, becoming
light by late this afternoon through Saturday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2...Fri and
Sat)...
The highlights are cold air, gusty winds, and snow returning to
Kodiak. First, the upper level Arctic trough sits on our doorstep
this morning. This feature is diving south across Alaska and
should clear through Southcentral from west to east today. Some
snow showers have developed overnight out of ahead of it. These
will continue to linger across the interior of the Kenai Peninsula
and the northern Gulf (to include Valdez). These showers could
cause brief reductions to visibility, but due to the speed of the
trough, any snow accumulations will be very limited. Snow will
linger through the day across the Copper River Basin with a few
inches of accumulation expected. As the trough moves past,
significantly colder and drier air will slide in. This is
evidenced by the Anchorage observation seeing its dewpoint fall
from 24 degrees to -8 degrees overnight. The cold air will also
produce gusty winds across much of the area, especially as it
reaches the typical outflow coastal locations (Valdez, Whittier,
Seward). Thompson Pass will see winds increase through the day
today as well. With some light snow continuing to fall, expect
periods of blowing snow to plague the pass, especially this
morning. By tonight, wind chills through the pass will drop off
sharply to dangerous levels near -35F degrees.

The gusty winds and sharp drop in temperatures continues to
produce hazardous marine conditions this morning. The primary area
of concern is near the Barren Islands and Shelikof Strait where
heavy freezing spray is likely. As outflow winds continue to ramp
up in many of the typical gap sites, be prepared for rapidly
building seas and freezing spray potential.

The other area of interest is Kodiak Island as we head into the
weekend. Several systems will pivot across the Northern Gulf of
AK. Each one will have the chance to bring precipitation to the
island. Conditions should start out cold enough to keep
precipitation type all snow for much of Sat. However, depending
on the exact track of a new area of low pressure and whether or
not the winds are coming off the warmer water, snow could mix with
(or turn over to) rain late Sat night into Sun. A Special Weather
Statement has been issued to highlight this uncertainty.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...

A upper level trough over the Southwest will usher in a cold
Arctic air mass over the region today. A wind chill advisory has
been issued for the Lower Kuskokwim Valley and Kuskokwim Delta
coast. Overnight low temperatures will drop tonight, ranging from
10 to 20 below. Across the Kuskokwim Delta, northerly winds will
increase this evening, creating wind chill values as low as 45
degrees below zero. This will be the trend again Saturday night
into Sunday as the airmass remains in place over the region.
Meanwhile, a front approaching the southwest coast today is
expected to weaken. Areas across the Alaska Peninsula, will see
easterly winds pick up this afternoon in response to the front.
Snowfall will spread in around the Bristol Bay region with only
minor accumulations expected. Precipitation should taper by early
Saturday as the front weakens significantly and moves inland. The
remainder of the weekend will be clear and cold, ahead of the next
front that tracks eastward late Sunday into Monday.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...

Weather over the Bering continues to be driven by a Kamchatka low
draping an occluded front over the central Bering. Southerly
flow and a rain/snow mix will continue across the central
Aleutians today while snow and blowing snow are in store for the
Pribilofs, where a Winter Weather Advisory has been issued through
this evening. As the front continues tracking eastward, conditions
over the Pribilofs will improve by the overnight hours, and
showers across the western Bering will fill in as cold air arrives
behind the front. Snow showers can also be expected across the
Aleutians for much of Saturday as colder, westerly flow returns.
The next systems arrives over the western Aleutians by Sunday
morning. This front looks to track much faster across the Bering
for the start of the next workweek.

&&

.MARINE (Days 3 through 5: Sunday through Tuesday)...

Bering Sea: Sub-gales and below 20 ft seas are likely Sunday.
Model agreement degrades into early next week. Multiple low
centers will interact over the western Bering. Winds exceeding 35
kt are possible but their location remains uncertain.

Gulf of Alaska: Westerly gales and seas greater than 20 ft are
likely in the southern Gulf on Sunday. These will expand northward
Monday and Tuesday, potentially strongest between Kodiak Island
and the Kenai Peninsula.

&&

.LONG TERM FORECAST (Days 4 through 7: Monday through Thursday)...

A low in the eastern Gulf will bring light precipitation to
eastern Prince William Sound and the Copper River Basin on Sunday.
Northwesterly offshore flow looks to persist elsewhere across
much of the mainland through Monday with weak high pressure over
the interior. This will bring clearer skies and cooler
temperatures across Southwest and Southcentral Alaska. There
remains some disagreement into Tuesday as the ECMWF displaces the
upper level ridge faster than the GFS or Canadian and overspreads
snow well into the Middle Kuskokwim Valley. In any case,
precipitation will track eastward across the state Wednesday
before an upper ridge builds in on Thursday. As usual, the Bering
looks to remain active under a series of lows and fronts.
Confidence remains good regarding the overall longwave pattern,
but details are still lacking.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...Winter Weather Advisory: 195.
		 Wind Chill Advisory: 152,155.
MARINE...Storm Warning: 130,131.
		 Gale Warning: 119,120,125,129,132,137-139,160,165,179,
 		 180,185,351,352,412,414.
		 Heavy Freezing Spray: 121,127,129,130,139,141,160,180,
		 185,414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AS
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KO
MARINE/LONG TERM...AP